Negative ion generator using an ultraviolet source to irradiate electrically conductive material



Apnl 7, 1964 c. ALLEN ETAL 3,128,378

NEGATIVE ION GENERATOR USING AN ULTRAVIOLET souRoE To IRRADIATE ELECTRICALLY CONDUCTIVE MATERIAL Filed Oct. 4, 1960 N N O O INVENTORS CHARLES L. ALLEN ALLEN R. TAYLOR ATTORNEY United States Patent OfiFice 3,128,378 Patented Apr. 7, 1964 NEGATIVE IQN GENERATQR USENG AN ULTRA- VEQLET 0URCE TO HRRADEATE ELECTRICAL- LY CQNDUCTIVE MATERIAL Charles L. Allen, West Englewood, and Allen R. Taylor, Nutley, Nl, assignors to Dynamics Corporation of America, New York, Nfih, a corporation of New York Filed Get. 4, 196b, Ser. No. 60,353 3 Claims. (Cl. 250-433) This invention relates to negative ion generators and more specifically to a means and method of generating negative ions through the use of irradiation of electrically conductive materials with an ultraviolet source of energy.

A great deal oi research is now being carried on by various scientific and medical institutions relative to the use of air containing a high concentration of negative ions. This research is directed to the use of such air in the treatment of various diseases, allergies, and mental attitudes involved in the held of physical and mental health. The results achieved so tar by such clinical tests indicate that negative ions have many beneficial eiiects on a majority of the subjects tested.

Although negative ions occur in nature to some extent, it has been found that they must be generated artificially in order to produce the quantity necessary to have any of the desirable results mentioned above.

Prior to the present invention artificial ions have been generated in three basic methods. One method is by generation from radioactive sources, which is natures method of producing negative ions. A second method of producing negative ions is through the use of a high voltage corona discharge. The third and most practical method to date is through the use of incandescent metals to produce thermionic emission. The latter devices employ a radioactive material, such as tritium, which is contained in a titanium toil and mounted on an electrode encased in a suitable dielectric guard. A potential is impressed on the electrode which separates the ions as desired. The desired unipolar ion is electrostatically directed away from the electrode by placing a charge on the electrode of the same polarity as the desired ion. Among other drawbacks of this method, is the fact that undesirable heat is produced together with the negative ions. Additionally, the quantity of negative ions produced is restricted by practical limits in the size of such a device.

Accordingly, the object of this invention is to provide a negative ion generator which will produce a large quantity of negative ions.

Another object of this invention is to provide a negative ion generator with substantially no heat production.

Yet another object of this invention is to provide a negative ion generator which will operate on normally avail-able commercial and domestic power supplies.

A further object of this invention is to provide a negative ion generator having few par-ts which is relatively inexpensive to produce.

A still further object of this invention is to provide a method of negative ion generation using photoelectric energization.

Further objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the drawings, wherein:

FIG. 1 is a sectional view of a' schematic representation of the present invention; and

FIG. 2 is a sectional view of the apparatus of FIG. 1 with an additional screen element therein.

Basically, the invention comprises a means and method of generating a large quantity of negative ions by means of irradiating an electrically conductive material susceptible to the passage of therethrough with a source of light energy loss than substantially 7000 A.

Electrically conductive materials emit electrons upon being subjected to irradiation from an energy source over a broad band of wavelengths. However, for practical purposes, a light source having a wavelength less than substantially 7000 A. would normally be used in practicing the present invention. Therefore, although any source of ultraviolet irradiation may be used, a practical source has been found to be the small ultraviolet lamps commercially produced and some of which are known as ozone or germicidal lamps. Ultraviolet radiation from these ultraviolet lamps cannot directly ionize air. About of the radiation emitted from these lamps is at a wavelength of 2537 A. A wavelength of 950 A. would be necessary for the first ionization potential of oxygen. However, the photoelectric threshold for many metals and compounds is less than 2537 A. radiation. Thus, by photoelectrically ejecting the electrons from the materials adjacent to the lamp, ions can be produced. The ejected electrons can attach themselves to oxygen, water vapor or dirt particles in the air to pro duce these ions.

FIG. 1 is a sectional view of a basic apparatus which may be used in practicing the present invention. A housing 11, which may be rectangular, square or circular encloses the ion generating equipment. This housing may be of any desired rigid material and it is shown herein as a metal or metal alloy material. A socket 13 is mounted within the enclosure 11 near one end thereof for providing electrical connections to an ultraviolet lamp 15. A material 17 susceptible to the passage of air therethrough is secured within the housing 11 adjacent to the ultraviolet lamp 15. This foraminous material may be a mesh or screen or the like. Best results are obtained when the screen is grounded such as through the screws 19 which hold the screen in place. At the other end of housing 11 is mounted a means for forcing air therethrough such as a fan or blower driven by motor 23 through shaft 24 with the direction of airflow indicated by the arrows.

The ultraviolet light source irradiates the screen 17 and photoolectrically ejects electrons therefrom. The electrons which are emitted from the screen collide with air molecules and produce negative oxygen ions. By forcing air past the lamp and through the screen 17 by means-of the tan 21, the negative ions are carried away from the screen and into the surrounding atmosphere outside of the housing 11.

It has been determined that all electrically conductive materials emit electrons upon being irradiated by an ultraviolet source. The quantity of electrons produced is dependent upon the work function of the particular elec trically conductive material and the intensity of the radia tion. As is well known, the work function of various conductive elements varies over a large range of values, and, therefore, the elements with the lowest work function produce the highest number of electrons when subjected to a similar ultraviolet source.

However, when the ion generator is to be used over long periods of time, a further factor should be considered. This factor is the activity of the particular element or elements used. A number of the elements with low work functions undergo a chemical reaction when exposed to air and accordingly produce electrons only for a very short period of time. Other elements tend to develop surface oxidation when exposed to air which creates an insulating material around the element and reduces its electron emission substantially. Accordingly, a material should be chosen which best meets both of the above mentioned requirements. The ideal choice would appear to be the inactive material having the lowest work function.

A third factor to consider is a means of insuring that the electrons produced from the screen have an opportunity to collide with the air molecules before they attach themselves to some other surface and that the resulting negative ions are dispersed in the atmosphere. This is accomplished by forcing the air through the material in the area where the electrons are being emitted due to the irradiation of the ultraviolet lamp. Again, practical aspects should be considered when determining the volume and velocity of the air to be used. These considerations control the size and mesh of the screen and the size of the fan. Although electrons will'be emitted from a solid element, such as a plate, when irradiated by an ultraviolet source, experiments have shown that the increase in production of electrons is of unusual proportions when a screen or mesh is used and air is'passed therethrough.

A standard procedure was used in testing the negative ion production of materials composed of various metals, metal alloys and metal platings. A plurality of flat metal plates were placed parallel to the direction of airflow and were enclosed within a rectangular conduit. Alternate plates were connected to a source of negative potential and the remaining plates were connected to an arnmeter in order to obtain a current reading which could be converted to negative ions per cubic centimeter. The following table shows the results of such test procedures. In these tests, three standard ultraviolet lamps were used and the screening was adjacent to the lamps. The conduit and fan were designed so as to produce a steady flow of air past the bulb and through the screen. These tests are included as representative of the ion production of relatively inactive materials. The following test results were obtained with an airflow of 50 c.f.m.

The resultant current readings can be converted to obtain the negativeions per cubic centimeter through the use of the following formula.

Negatlve Ions/cc 1.6 c.f.m. X 28,320

In the above tests the material'was placed adjacent to the ultraviolet lamp in order to obtain the maximum emission of electrons from the material. This is'essential only when a low energy source'of ultraviolet light is used since a very high energy source could feasibly irradiate the material to a degree wherein saturation of the screen L would occur and any greater amount of energy would not increase the electron emission. Accordingly, ifa high energy source of ultraviolet were used, the source would not necessarily be required to be immediately adjacent to the material emitting the electrons.

Additionally, the location of the fan and the bulb and the screen relative to each other may be changed. However, the relative location as'shown in the drawings appears to be preferable for several reasons. By maintaining the fan upstream from the bulb and the screen, the negative ions are free to pass into the outer atmosphere with no further obstructions. If the fan is placed downstream from the screen and the bulb, there is a tendency for the fan to absorb some of the negative ions before they have an opportunity to reach the outer atmosphere. Also, by placing the lamp upstream from the screen an apparent air foil takes place and the air is directed around the lamp and through the screen at the point where maximum irradiation occurs.

It is to be understood that additional lamps may be used on the same side of the screen as well as on the opposite side of the screen and the screen may be shaped in any desired manner so as to conform to the number and shape of the lamps. Also, any standard reflectors could be used to direct the maximum amount of radiation from the lamps onto the screen. It is also noted that the material may be of an alloy and may also be of a non-emitting base with an emitting material plated thereon. This is true since the emission of electrons occurs only at the surface of the irradiated material.

There is shown, in FIG. 2, a sectional view of the apparatus of FIG. 1 with an additional screen or mesh 27 secured to the housing between the ultraviolet lamp 15 and the fan 21. Screen 27 may be secured to the housing by means of screws 29 insulated from the housing 11 by a plastic plug 31 or the like. The screen 27 is insulated from the housing 11 in order that it may be maintained at a potential which is positive with respect to the emitting screen 17. It has been found that the use of such a screen will increase the total negative ion output of the device by as much as 30%. This is apparently due to the fact that the positive screen 27 tends to draw more electrons out of the emitter screen into the air path and, although it may tend to collect some of these electrons, the resultant increase in negative ion production indicates the advantages of its use. The increase may also be due in part to an apparent increase in the velocity of the electrons between the emitter screen and the positive potential screen 27.

Screen 27 may also be of any electrically conductive material, but it appears that the use of a metal having a high secondary emission, such as nickel, is preferable. Although the distance between the screen 27 and the ultraviolet lamp 15 is not particularly critical, tests have indicated that when the screen is placed a distance from the bulb approximately equal to the width of the bulb excellent results are obtained. It should be noted that the major requirement of the particular device as shown in FIG. 2 is that the screen 27 be maintained at a potential positive with respect to the screen 17. Obviously, the screen 27 could be maintained at ground potential and the screen 17 maintained at a negative potential with the same results. Of course, the necessary insulation between the screen 17 and the enclosure 11 would have to be used in such an arrangement.

While the principles of the invention have been described above in connection with specific embodiments thereof, it is to be clearly understood that this description is made only by way of example and not as a limita-' tion on the scope of the invention.

We claim:

1. A negative ion generator comprising a first electrically conductive metallic mesh and an ultraviolet source directly irradiating substantially all of said mesh for photoelectrically ejecting electrons from said mesh, means for passing air through said mesh, and a second electrically conductive metallic mesh between said first named mesh and said means for passing air therethrough, said second mesh being maintained at a potential which is positive with respect to said first mesh.

2. A negative ion generator comprising a first electrically conductive metallic foraminous material, an ultraviolet light source in close proximity to said material directly irradiating said material for photoelectrically ejecting electrons therefrom, means for passing air through said material, and a second electrically conductive foraminous material disposed between said first named material and said means for passing air through said first material, said second material being maintained at a potential positive with respect to said first material.

3. A negative ion generator comprising a housing having a passage therethrough, a first electrically conductive metallic screen within said passage at one end of said housing and substantially covering one end of said passage, a fan within said passage at the other end of said 5 housing for forcing air past said screen, an ultraviolet light source between said fan and said first screen, and a second electrically conductive screen between said fan and said light source, said second screen being maintained at a positive potential with respect to said first 5 named screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,449,681 Wilson Sept. 21, 1948 10 

3. A NEGATIVE ION GENERATOR COMPRISING A HOUSING HAVING A PASSAGE THERETHROUGH, A FIRST ELECTRICALLY CONDUCTIVE METALLIC SCREEN WITHIN SAID PASSAGE AT ONE END OF SAID HOUSING AND SUBSTANTIALLY CONVERING ONE END OF SAID PASSAGE, A FAN WTIHIN SAID PASSAGE AT THE OTHER END OF SAID HOUSING FOR FORCING AIR PAST SAID SCREEN, AN ULTRAVIOLET LIGHT SOURCE BETWEEN SAID FAN AND SAID FIRST SCREEN, AND A SECOND ELECTRICALLY CONDUCTIVE SCRREEN BETWEEN SAID FAN 